Updated at 7:45 p.m. Wednesday with additional comments from district and city leaders.

Citing security concerns, Richardson ISD is canceling classes on Election Day when some of its schools will serve as polling places.

An email sent to parents Wednesday said the "change is being made as a precaution" because too many people will have access to the schools during voting Nov. 6. The cancellation announcement didn't directly reference school shootings, but comes as districts consider beefing up security measures and offering more counseling services after recent deadly attacks.

Richardson ISD spokesman Chris Moore said the community wanted to be extra cautious about student safety.

"We have thousands of people who enter our campuses," Moore said of Election Day. "And while we can monitor that while they're in there ... we can't run background checks on everyone who shows up to vote."

Moore said Nov. 6 will be a staff development day. The district — which covers a politically and racially diverse area where more than half of students come from low-income families — will take special precautions to keep voters away from staff members and daytime care students who will be in schools on Election Day.

In McKinney, parents have come before school board trustees advocating for metal detectors in schools. Others have called for a greater emphasis on mental wellness to address what they say is one of the root causes of school violence.

District leaders have expressed concerns about installing metal detectors in schools, specifically because of the financial and personnel resources needed for the effort. The machines would also affect the flow of students into school.

McKinney ISD spokesperson Cody Cunningham said during a June board meeting that it's a misconception that metal detectors are a foolproof way to keep guns out of schools. He pointed out students could become more vulnerable while waiting to go through the metal detectors.

"This is not to say they don't work. This is to say, 'Have we created another safety issue? And if so, how are we doing to address that situation?'" he said.

Security concerns prompted Frisco ISD to put $2 million in its budget for dozens of new staffers to free up counselors to spend more time with students. The district also will add a district emergency manager and five crisis counselors to the high school feeder program.

Frisco ISD has budgeted another $1.6 million to add more security, safety and counseling intervention staff. The district also subscribed to a new mobile app to accept anonymous tips about safety, bullying and other issues.

Moore, Richardson ISD's spokesman, said district officials had talked aboutmaking future Election Days student holidays during the 2016 presidential election. School board trustees in May discussed the issue when setting the 2019-20 school year calendar and approved to give students the day off on Election Day then.

"And then from the community, some of the feedback on that calendar was 'Why don't we do it this year, too?'" Moore said.

He said the change to the upcoming school year calendar was an administrative recommendation proposed to the school board in June. Trustees agreed to the change, but didn't take an official vote, he said. Moore said the district has scheduled enough class time to avoid a make-up day.

A previously scheduled student holiday on Oct. 5 will remain unchanged, the district said.

Having Election Day off could also give students an opportunity to go to the polling place with their parents, said Dallas City Council member Adam McGough, whose district includes Richardson ISD boundaries.

The move isn't unprecedented. Schools in several states canceled classes on Election Day in 2016.

But several other large North Texas districts said they don't expect to follow Richardson's lead. A Plano ISD spokeswoman said canceling classes isn't under consideration currently. Arlington ISD schools will remain open for Election Day, and Garland ISD hadn't made any plans to cancel classes Nov. 6, a spokeswoman said.

Dallas ISD is also unlikely to do so.

"Knowing who we are as a large urban school district, I don't see us making that amendment," said Dallas ISD spokeswoman Robyn Harris. "So many of our families rely on us to have school open each and every day."

On voting days — especially when there's a contentious issue on the ballot — schools and administrative sites used as polling places get extra patrol from both Dallas ISD police and other local law enforcement, she said.